Battery management circuit and related techniques using MOSFET power switch with intelligent switch control

Abstract

A circuit includes a power supply configured to generate a supply voltage, an electrical load coupled to receive the supply voltage from the power supply, and a switching circuit. The switching circuit has a first terminal coupled to a first terminal of the electrical load, a second terminal, and a control terminal. The first terminal and the second terminal of the switching circuit correspond to current conducting terminals of the switching circuit. The circuit also includes a current sensing circuit and at least one battery having a first terminal coupled to a corresponding terminal of the current sensing circuit. The circuit additionally includes a battery measurement circuit having a first terminal coupled to the control terminal of the switching circuit and at least a second terminal coupled to the first terminal and a second terminal opposing the first terminal of the at least one battery.

What is claimed is: 
     
       1. In a system including a power supply configured to generate a supply voltage, an electrical load configured to receive the supply voltage, a battery pack comprising at least one battery and a battery management circuit for managing the battery pack, the battery management circuit having a first terminal and a second terminal configured to be coupled to two opposing terminals of the power supply and two opposing terminals of the electrical load, and having a third terminal and a fourth terminal configured to be coupled to two opposing terminals of the at least one battery, the battery management circuit comprising:
 a switching circuit having a first terminal coupled to the first terminal of the battery management circuit, a second terminal, and a control terminal; 
 a current sensing circuit having a first terminal coupled to the second terminal of said switching circuit, a second terminal coupled to the control terminal of said switching circuit, and a third terminal coupled to the third terminal of the battery management circuit, said current sensing circuit configured to receive a current signal from said switching circuit, measure a direction of the current signal, and provide a current sensing signal indicative of the direction of the current signal at the second terminal of said current sensing circuit; and 
 a battery measurement circuit having a first terminal coupled to the control terminal of said switching circuit and at least a second terminal coupled to the first and second terminals of the at least one battery, said battery measurement circuit configured to measure one or more characteristics of the at least one battery and provide a battery measurement signal in response thereto at the first terminal of the battery measurement circuit, wherein a control signal corresponding to the current sensing signal and the battery measurement signal controls current flow through the first terminal and the second terminal, that provide current conducting terminals, of said switching circuit. 
 
     
     
       2. The battery management circuit of  claim 1  wherein the one or more characteristics include open circuit voltage and/or open circuit voltage behavior of the at least one battery. 
     
     
       3. The battery management circuit of  claim 2  wherein said battery measurement circuit determines state of charge (SOC) and/or state of health (SOH) characteristics of the at least one battery in response the measured open circuit voltage and/or open circuit voltage behavior of the at least one battery. 
     
     
       4. The battery management circuit of  claim 1  further comprising:
 a logic gate having a first input coupled to the second terminal of said current sensing circuit, a second input coupled to the first terminal of the battery measurement circuit, and an output coupled to the control terminal of said switching circuit; said logic gate configured to receive the current sensing signal from said current sensing circuit and the battery measurement signal from said battery measurement circuit at the first input and the second input thereof and in response thereto provides a logic gate output signal at the output thereof, wherein the logic gate output signal controls current flow through the current conducting terminals of said switching circuit. 
 
     
     
       5. The battery management circuit of  claim 1  further comprising:
 a switch control circuit having an input coupled to the second terminal of said current sensing circuit and an output, said switch control circuit configured to receive the current sensing signal at the input thereof and in response thereto produce a switched output signal at the output thereof; and 
 a logic gate having a first input coupled to the output of said switch control circuit, a second input coupled to the first terminal of said battery measurement circuit, and an output coupled to the control terminal of said switching circuit; said logic gate configured to receive the switched output signal and the battery measurement signal at the first input and the second input thereof and in response thereto provide a logic gate output signal at the output thereof, wherein the logic gate output signal controls the current flow through the current conducting terminals of said switching circuit. 
 
     
     
       6. The battery management circuit of  claim 1  wherein said switching circuit comprises a field-effect transistor (FET) having a source terminal, a drain terminal and a gate terminal, wherein the source terminal corresponds to the first terminal of said switching circuit, the drain terminal corresponds to the second terminal of said switching circuit, and the gate terminal corresponds to the control terminal of said switching circuit. 
     
     
       7. The battery management circuit of  claim 6  wherein the field-effect transistor is provided as a metal-oxide-semiconductor field-effect transistor (MOSFET). 
     
     
       8. The battery management circuit of  claim 7  wherein the MOSFET is provided as an enhancement mode MOSFET. 
     
     
       9. The battery management circuit of  claim 7  further comprising:
 at least one diode having a positive terminal and a negative terminal, wherein the positive terminal is coupled to the first terminal of said switching circuit and the negative terminal is coupled to the second terminal of said switching circuit. 
 
     
     
       10. The battery management circuit of  claim 9  wherein said at least one diode is provided as a p-n junction diode. 
     
     
       11. The battery management circuit of  claim 9  wherein said at least one diode is provided as a parasitic diode integrated into the MOSFET, a discrete diode or a combination thereof. 
     
     
       12. The battery management circuit of  claim 1  wherein said battery measurement circuit is provided as part of a controller, wherein said controller is configured to provide the battery measurement signal. 
     
     
       13. A circuit comprising:
 a power supply having a first terminal and a second terminal, which are two opposing terminals, said power supply configured to generate a supply voltage; 
 a electric load having a first terminal coupled to the first terminal of said power supply and a second terminal, which is opposing the first terminal and coupled to the second terminal of said power supply, said electrical load configured to receive the supply voltage from said power supply; 
 a switching circuit having a first terminal coupled to the first terminal of said electrical load, a second terminal, and a control terminal, wherein the first terminal and the second terminal provide current conducting terminals of said switching circuit, said switching circuit including:
 a plurality of metal-oxide-semiconductor field-effect transistors (MOSFETs), each MOSFET of said plurality of MOSFETs having a source terminal, a drain terminal and a gate terminal, wherein the source terminals of said plurality of MOSFETs are coupled to the first terminal of said switching circuit, the drain terminals of said plurality of MOSFETs are coupled to the second terminal of said switching circuit, and the gate terminals of said plurality of MOSFETs are coupled to the control terminal of said switching circuit; and 
 a plurality of diodes, each diode of the said plurality of diodes having a positive terminal and a negative terminal, wherein the positive terminals of said plurality of diodes are respectively coupled to corresponding ones of the source terminals of said MOSFETs and the negative terminals of said plurality of diodes are respectively coupled to corresponding ones of the drain terminals of said MOSFETs; 
 
 a current sensing circuit having a first terminal coupled to the second terminal of said switching circuit, a second terminal coupled to the control terminal of said switching circuit, and a third terminal, said current sensing circuit configured to receive a current signal from the second terminal of said switching circuit at the first terminal thereof, measure a direction of the current signal, and provide a current sensing signal corresponding to the direction of the current signal in response thereto at the second terminal of said current sensing circuit; 
 at least one battery having a first terminal coupled to the third terminal of said current sensing circuit and a second opposing terminal coupled to the second terminal of said electrical load; and 
 a battery measurement circuit having a first terminal coupled to the control terminal of said switching circuit and at least a second terminal coupled to the first terminal and the second terminal of said at least one battery, said battery measurement circuit configured to measure one or more characteristics of said at least one battery and provide a battery measurement signal in response thereto at the first terminal of said battery measurement circuit, wherein a control signal corresponding to the current sensing signal and the battery measurement signal controls current flow through the current conducting terminals of said switching circuit. 
 
     
     
       14. The circuit of  claim 13  wherein in response to measuring the direction of the current signal, said current sensing circuit further provides a corresponding current sense control signal to a third terminal of said battery measurement circuit to control measurement of the one or more characteristics of said at least one battery, and measurement of current flow rate, and charge into and out of the at least one battery by said battery measurement circuit. 
     
     
       15. The circuit of  claim 13  wherein the plurality of MOSFETs is five MOSFETs. 
     
     
       16. The circuit of  claim 13  further comprising:
 a logic gate having a first input coupled to the second terminal of said current sensing circuit, a second input coupled to the first terminal of said battery measurement circuit, and an output coupled to the control terminal of said switching circuit; said logic gate configured to receive the current sensing signal from the second terminal of said current sensing circuit and the battery measurement signal from said battery measurement circuit at the first terminal and the second terminal thereof and in response thereto provide a logic gate output signal at the output thereof; and 
 an opto-isolator circuit having an input coupled to the logic gate output and an output coupled to the control terminal of said switching circuit, said opto-isolator circuit configured to receive the logic gate output signal at the input thereof and in response thereto provide an opto-isolator circuit output signal at an output thereof, wherein the opto-isolator circuit output signal controls current flow through the current conducting terminals of said switching circuit. 
 
     
     
       17. The circuit of  claim 13  wherein said battery measurement circuit includes a current source and a ballast resistor, and the current source and the ballast resistor are used by said battery measurement circuit to measure an internal resistance of said at least one battery. 
     
     
       18. The circuit of  claim 13  wherein said current sensing circuit is further configured to measure magnitude and polarity of the current signal, and the current sensing signal is further indicative of the magnitude and the polarity of the current signal. 
     
     
       19. The circuit of  claim 13  wherein said switching circuit, said current sensing circuit, and said battery measurement circuit are provided as part of a battery management circuit for managing the at least one battery. 
     
     
       20. The circuit of  claim 13  wherein each MOSFET of said plurality of MOSFETs is provided as an enhancement mode MOSFET.